Plant diseases caused by fungi and mites have a significant adverse impact on the production of important crops worldwide.
Pest mites belong to two main families. The most important family is Tetranychidae, also known as the spider mites. These mites cause widespread damage to almonds, apple, avocado, cassava, citrus, cotton, grapes, tea, various greenhouse crops like cucumber, pepper and tomato, and several ornamentals, including roses and chrysanthemums [Helle, W. & Sabelis, M. W. Spider Mites, Their Biology, Natural Enemies and Control, Volumes. I and II, Elsevier, Amsterdam (1985)]. The other family, Eriophyidae, corresponds to the rust or gall mites, which can be major pests of apple, citrus, coconut, pear, currants and berries, as well as many vegetables and ornamentals [Lindquist et al. (Eds.) Eriophyoid Mites, Their Biology, Natural Enemies and Control. Elsevier, Amsterdam (1996)]. The carmine spider mite, Tetranychus cinnabarinus, and the citrus red mite, Panonychus citri, belong to the former family, whereas the citrus rust mite, Phyllocoptruta oleivora, to the latter. In Israel, the carmine spider mite is an important pest of vegetables and ornamentals, whose chemical control has met increasing difficulties due to evolving resistance to pesticides. The citrus red mite is of minor importance, whereas the citrus rust mite is the major pest of citrus in Israel and many other parts of the world. Local citrus growers have been encountering serious problems in the chemical control of the citrus rust mite, due to its increased resistance to acaricides and the presence of pesticide residues on exported fruit [Palevsky et al. Mite problems on citrus and control strategies in Israel. Proceedings of the International Congress of Citriculture, (in press)]. In counterpart, biological control of this pest with introduced predators has just begun and is still uncertain [Argov, Y., S. Amitai, G. A. C. Beattie and U. Gerson. Rearing, release and establishment of imported predatory mites to control citrus rust mite in Israel. BioControl, 47: 399-409 (2002)].
Likewise, fungal phytopathogens cause major and severe economic losses in the agricultural and horticultural industries. Germination and growth of infected plants are inhibited; plants succumb to soft rot and may even die. Infested soils are unsuitable for growing certain crops. The powdery mildews are the most common, widespread and easily recognizable plant diseases. They are caused by fungi of the family Erysiphaceae, which are grouped into seven main genera [Agrios, G. N. Plant Pathology, 4th ed. Academic Press, New York (1997); Braun, U. A Monograph of the Erysiphales (Powdery Mildews), J. Cramer, Grebruder Borentraeger, Berlin (1987)]. Powdery mildews are characterized by spots or patches of a white to grayish powdery growth on young plant tissues, which can cover entire leaves and other organs of the plant [Agrios (1997) id ibid.]. Powdery mildews are very often present on crop plants and ornamentals, and the yield losses that they incur annually on all crops probably surpasses the losses caused by any other single type of plant disease. Crops that suffer severely from powdery mildews include wheat, barley, cucumber, squash, strawberry, grape, apple, mango, ornamentals such as rose, begonia, lilac and many others [Agrios (1997) id ibid.]. Chemical fungicides usually control these diseases, but this mode of control is continuously being challenged by the rapid development of resistance to the recommended fungicides. As for the mites pest, biological control of fungal phytopathogens is just in its infancy as well. Although the biofungicide AQ10 has been registered for powdery mildews control since 1996, the extent of its use is still moderate when compared to the use of chemical fungicides [Copping, L. G. (Ed.) The BioPesticide Manual, 1st ed. British Crop Protection Council, Farnham (1998); Sztejnberg et al. Ampelomyces quisqualis for biological and integrated control of powdery mildews in Israel. J. Phytopathology 124:285-295 (1989)]. Overall, world expenditure for fungicides to control powdery mildews is estimated to be circa one billion US dollars per year.
In summary, plant mites and fungal phytopathogens are still mostly controlled with chemical acaricides and fungicides, despite the above-mentioned corollary problems. Thus, the widespread abuse of pesticides and the emergence of pest resistance to most of these chemicals has increased the demand for environmentally-friendly biological pesticides, or “biopesticides” [Copping, 1998, id ibid.].
In order to fulfill this demand, it is a major object of the invention to provide new species of fungi that possess activity against plant mites and fungi, and that can be used against them. Another object of the invention is to provide anti-fungal and anti-miticidal preparations, or biopesticides.
So far, there has been no indication that any of the three new fungal species hereby described and claimed, have had any adverse effect on the plants with which they were in contact in any way, nor were they detrimental to any other organism (except the pests being assayed against). It is therefore a further object of the invention to provide miticidal and fungicidal compositions that would be devoid of adverse effects on the treated plants, or on the environment.
These and other objects of the present invention will become apparent as the description proceeds.